Overcenter spring operating mechanism for an electric circuit breaker



4 Sheets-Sheet 1 P. C. NETZEL Nov. 25, 1958 Filed Dec. 9, 195'?Inventor: Philip C. Netzel',

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OVERCENTER SPRIN ATING MECHANISM FOR AN ELECTRI CIRCUIT BREAKER FiledDeo. 9, 1957 v 4 Sheets-Sheet 2 Inventor:

Nov. 25, 1958 P. c. NETZEL 2,862,075

OVERCENTER SPRING OPERATING MECHANISM FOR AN ELECTRIC CIRCUIT BREAKERFiled Deo. 9, 1957 4 Sheets-Sheet 3 Inventor: Phi ip C. Netzel,

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Nov. 25, 1958 P. c. NETZEL OVERCENTER SPRING OPERATING MECHANISM FOR ANELECTRIC CIRCUIT BREAKER 4 Sheets-Sheet 4 Filed Dec. 9, 1957 In Venter:philip C. etzel be His ttorneg.

United States Patent O GVERCENTER SPRING OPERATING MECHANISM FOR ANELECTRIC CIRCUIT EREAKER Philip C. Netzel, Swarthmore, Pa., assigner toGeneral Electric Company, a corporation of New York Application December9, 1957, Serial No. 701,591

5 Claims. (Cl. 20D-70) This invention relates to an overcenter springoperating mechanism for an electric circuit breaker, and it relates moreparticularly to a circuit breaker operating mechanism wherein anovercenter spring is employed to obtain a snap-action circuit closingoperation.

Overcenter spring mechanisms are commonly used for closing and openinglow-voltage air circuit breakers having relatively low current ratings.A typical operating mechanism of this type comprises a toggle having oneend connected to the movable switch member of the breaker, latchingmeans supporting the other end of the toggle, an overcenter tensionspring connected at one end to the knee of the toggle, and means formoving the other end of the overcenter spring in a manner to producesnapaction switch closing movement of the toggle. When a conventionalmechanism such as this is applied to circuit breakers having relativelyhigh current ratings, it is necessary to use very strong and heavyovercenter springs, that is, springs having a relatively high springconstant. This is because a large amount of force is required toovercome static friction and inertia of the relatively massive contactstructure and related movable linkages of such high current breakers.Since there is a practical limit to the amount of available space inwhich the operating mechanisms for such breakers can be mounted, thenecessary closing force cannot conveniently be obtained by stretching orextending relatively weak springs over a relatively long distance.

The use of relatively heavy and strong overcenter springs in the closingmechanisms of circuit breakers is undesirable for at least two reasons.In the first place, a great deal of force is required while closing thebreaker to charge such a spring, that is, to elongate the spring priorto the snap-action closing operation. This is particularly undesirablewhen the breaker is arranged to be closed manually. Furthermore, boththe wear and the possibility of damage to the moving parts of thebreaker are increased in proportion to the amount of closing forceemployed; Accordingly, it is an object of this invention to provide animproved overcenter spring operating mechanism wherein spring force issupplemented by means permitting the use of a weaker overcenter springthan would otherwise be possible.

Another, object of the invention is the provision, in an overcenterspring closing mechanism for an electric circuit breaker, of meansarranged to aid the overcenter spring in overcoming static friction andinertia of the movable breaker parts.

Still another object of the invention is to provide an overcenter springoperating mechanism so constructed and arranged that the overcenterspring which is moved to initiate snap-action closing cannot be movedeffectively to initiate breaker opening or tripping.

In carrying out my invention in one form, I provide a circuit breakeroperating mechanism comprising a toggle connected to close the circuitbreaker contacts, an operating member movable between irst and secondpositions,

2,862,075 Patented Nov. 25, 1958 and an overcenter tension springcoupled to both the toggle and the operating member and effective inresponse to movement of the operating member from its first to itssecond position to produce snap-action contact closing movement of thetoggle. I also provide rigid means movable with the operating member andengageable with the toggle so arranged as to initiate movement of thetoggle while the operating member is being moved between its rst andsecond positions and before the overcenter spring becomes effective.

In one embodiment of my invention, the rigid means l is arranged toengage the toggle and start contact closing movement thereof as theoperating member approaches its second position, whereby it isunnecessary for the overcenter spring to supply sufficient force toovercome static friction and the inertia of the toggle, the contacts andthe related movable parts. In a second embodiment of the invention, therigid means is disposed to engage the toggle at an earlier point in theclosing operation, and the toggle is then moved to an intermediateposition where it is held by a suitable blocking member. The blockingmember is actuated as the operating member approaches its secondposition to release the toggle and permit snap-action contact closingmovement thereof. In the intermediate position of the toggle, the forcesresisting closing movement are less and the moment of the force suppliedby the overcenter tension spring is increased, whereby a relatively weakovercenter spring may be used to obtain successful breaker closing.

In another aspect of my invention, the toggle, operating member andovercenter spring are so arranged that after the circuit breaker hasbeen closed, movement of the l from the following description taken inconjunction with pivot 14 suitably supported on the base 12. A compresa.

the accompanying drawings in which:

Fig. l is a side elevation of a circuit breaker having an operatingmechanism constructed in accordance with one embodiment of my invention,the circuit breaker being shown in its closed circuit position;

Fig. 2 is a section taken along lines 2---2y of Fig. l;

Fig. 3 is an exploded perspective view, partly in section, of thebreaker operating mechanism shown in Fig. l;

Fig. 4 is a view similar to that of Fig. l but with the circuit breakerand the operating mechanism being shown in an open circuit position;

Fig. 5 shows the mechanism in its reset position;

Fig. 6 shows the mechanism in a position through which it passes afterresetting and shortly before snapaction closing operation takes place.

Fig. 7 is a simplified side elevation of a circuit breaker operatingmechanism constructed in accordance with a second embodiment of myinvention, the mechanism being shown in a position through which itpasses after resetting and at -a relatively early stage in the closingoperation; and

Fig. 8 is `a view of the Fig. 7 operating mechanism in its closedcircuit position.

Referring now to Fig. l, I have shown a circuit breaker comprising aframe member for mounting a base member indicated generally by thereference numbers 11 and 12, respectively. A relatively stationarycontact 13 is mounted for slight pivotal movement on a stationary 3 sionspring biases Contact 13 counterclockwise about its pivot, as is shownin Fig. 1. A cooperatingY movable contact or switch member 16jis mountedfor pivotal movement about` a stationary pivot 17 which isl suitablysupported on the base 12. A stop 18AV mounted on frame 11 determines theopen circuit position of' contact 16 (see Fig. 4), and pivotal movementofA contact 16( in a clockwise direction carries this contact intocircuit making engagement with the stationary Contact 13 therebycompleting the circuit represented by conductors 19 and 20 in Fig. l..Thec'oinpression spring 15 permits contact 13 to/yield slightlyduringthe circuit'closing operation, thereby providing a wiping actionbetween the two cooperating contacts. i

The switch Contact ormember 16 isl moved between its open circuit andclosed circuit positions by means of a series of force and motionamplifying members and linkages indicated generally by the referencenumber 21 in Fig. 1. The interconnected linkages and members 21comprise, for example, a member 22 pivotally mounted Ion base 12' andconnected by` aylink 23 to the switch member 16, and a' pair ofidentical 3-sided members 24 and 25 pivotally mounted on frame 11 andconnected to the member 22` by a pair of links 26' and 27 As best seenin the perspective view Fig. 3, the pair of links 26 and 27 areinterconnected with the pair of members 24 and 25 by means of a pin 28laterally extending between members 24'and 25. The' members 24 and 25are pivot.- ally supported on' a common rod or shaft 29 fixed to theframe 11.

' The movement of the force and motion amplifying means 21l iscontrolled by a toggle 3() which is pivotally pinned at 31 to themembers 24 and 25. The toggle 311 comprises one pair of identical links32 and 33 which are connected to another pair of identical links 34 and35 by means of a laterally extending pin 37 best seen in Fig. 3. Pin 37forms the knee of the toggle. One end of links-32, 33 is connected bymeans of the pin 31 to the linkages and members 21 and hence to themovable switch' member 16. The' opposite end 38 of the toggle links 34,35 is connected to a pin 39 which is carried by a pair of generallyC-shapcd guide members 411 and 41. The guides 45.3 41 form part of alatching means which releasably restrains the end 38 of toggle 311 in alatched position. `In the closed circuit position of the switch member16, as is shown in Figs. 1, 2, 3 and 8, toggle end 38 is held in itslatched position and the toggle knee 37 assumes a position determinedbya shoulder 36 of the upper end `of the guides 41), 41. The guides 40, 41and the links 32, 33'of toggle 30 are respectively disposed in the sameplanes, and as'isfmost clearly indicated in Fig. 3, upward` movement ofthe toggle knee 37 is stopped by the links'3'2, 33 engaging the shoulder36 of guide members 40,'y 41.

Thelatching means for the toggle end 38 includes the pair of guides 40and 41 and a latch 42 disposed laterally intermediate the guides. Asbest seen in Fig. l, the guides 40, 41 are pivotallyV supported atltheir upper end on a rod .43y which is fixed to the circuit breakerframe 11. Spanning the other ends of the C-shaped guides 4t), 41 is aroller 44 which cooperates with the free end of latch 42. The latch 42is'pivoted at' one end on a rod 45 xed to the frame 11 as shown in Fig.2. As is clearlyl indicated in Fig. l, a tension spring 46 is providedto bias latch 42 clockwise about pivot 45 into engagement with theroller 44of the guides 40,41. -In the closed cir` cuit and resetpositions of the operating mechanism, the roller 44 is releasablyrestrained in an appropriate notch 47 in latch 42, whereby guides 40, 41hold the toggle end 38 in its latched position.

t As will become apparent hereinafter, the force exerted by the guides40, 41 through roller 44 `on the cooperating surface of notch 47 tendsto pivot latch 42 counterclockwise on rod 45, buta prop 48 isv provided,as is clearly shown in Fig. 1, to prevent such counterclockwisemovement. The prop 48 is fixed at one end to a trip shaft 49. Suitablemeans are provided to biasV the prop 48 into a latching position whereinthe free end ofthe prop engages ya roller 50 mounted on latch 42 toreleasably hold the latch and prevent counterclockwise motion thereof.

Guide releasing operation of the latch 42 is initiated by rotating tripshaft 49 in a counterclockwise direction which removes prop 48 fromroller 50 and permits counterclockwise movement of latch 42. Thecounterclockwise rotation of trip shaft 49 can be achieved by any numberof well-known means, either electrically or manually. For example,manually moving the paddle 51 shown in Fig. l in the direction of thearrow will accomplish the desired result. When latch 42 movescounterclockwise and releases guides 40, 41 in the manner describedabove, the guides will pivot about rod 43 in a clockwise direction fromthe iirst position shown in Fig. 1 to a second position shown in Fig. 4,thereby initiating a circuit opening operation. A

To provide breaker opening and closing force, a pair `of overcentertension springs 52 and 53 are provided. One end of each of these springsis connected' to the toggle 30 preferably at knee 37. The other ends ofsprings 52, 53 are secured by means of a pin 55 to apir of operatingmembers 56 and 57, best seen in Fig. 3'. i-EachI of the operatingmembers 56, 57 is mounted for pivotal movement' on the rod 253 which issupported by frame 1'1 The operating members arem'ovable about pivot29"y be-' tween first and' second' positions at opposite ends of theirnormal range of movement. The operating members 56 and 57 are inftheirsecond position in Figs; 1, 3, 4' and 8 vvhil'e in Fig". 5 they areshown in the rst position. l

For moving" the operating members 56, 57 between the first and secondpositions, a handle mechanism, indieated generally by reference number53 in Fig. l, is'provided. The handle mechanism comprises a shaft 5 9"which' is journaled in a stationary escutcheon plate 6) fixed to frame11. Ancho-red to the outer end of the shaft 59 is a handle member 61which is manually operable to elfe-ct limited rotation of the shaft 59.Anchored to the inner end of the shaft 59 is a crank 62 having at itsradially outer end an axiallyextending crankpin 63. A tie bar 64positively couples crankpin 63 to a laterally extending pin 65 whichbridges the operating members 56 and'57`, as best seen in Figs. 2 and 3.`It will be under! stood by those skilled in the art that the handlemechanism 58 has been shown merely for the sake of illustratic-n andthat other means', such as a solenoid for example, could be coupled topin 65 in order to move the operating members 56, 57.

Rotary movement of the handle member 61 carries the operating members56, 57 between their first and secondpositions. Such pivotal movement ofthe operating members will carry pin 55, to which one end `of theovercenter springs 52, 53`is attached, through an arc indicated byreference number 66 inA Figs. l, 6 and 7. It can be observedv in Fig. lthat the toggle 36 is' stopped in a position, as determined by shoulder36 of guidesY 4Q, 41, such that pivotal movement of the operatingmembers 56, 57 from their second to their iirst positions will not carrypin below the extended centerline of toggle links 34, 35. in otherwords, the centerline of links 34, 35 does not intersect the arc 66.This means that with the circuit breaker in its" closed cir-cuitposition, force exerted by the over-center springs 52, 53 will alwaysmaintain the toggle 39 in its Vstopped position shown in Fig. l, even ifthe operating members 56, 57 were moved to their first position.

In accordance with my invention, suitable holding means are providedtorestrain or block the operating members 56, 57 in` their second positionwhen the circuit breaker is closed. As can be seen in Fig; l, theholding :means comprises, for example, a hook-likecatch 67havingiarecessed portion 68 and mounted for pivotall movement on a shaft69 ixed to fra'nie 11. A suitablef spring 70 is provided to bias catch67 into engagement with a 'stop pin 71 that is also fixed to frame 11.The movable catch 67 cooperates` with the laterally extending pin 55carried by operating members 56, 57 to restrain or hold the operatingmembers in their second posltion.

The operating members are released or unblocked -when the circuitbreaker is open. Whenever the tripping shaft 49 is rotated to unlatchthe toggle and permit circuit opening operation (which operation will beexplained in detail hereinafter), the guides 40, 41 move pivotally aboutrod 43 in a clockwise direction to their second position determined bystop pin 71 which is engaged by an enlarged roller 72 disposed on thepin 39 extending between the guides 4t) and 41. See Figs. 3 and 4. Butbefore engaging the stop pin 71, roller 72 engages a camming surface 73located on the under side of catch 67 thereby pivoting the catchclockwise against its bias and lifting it clear of the operating memberpin 55, as is most clearly shown in Fig. 4. In this manner, theoperating members are unblocked or released upon opening of the circuitbreaker.

In order to return the guides 40, 41 to their first position whenresetting the operating mechanism (which resetting opcration will bedescribed in detail hereinafter) a laterally extending pin 74 isconnected between the operating members 56 and 57. This pin engages theupper surface 75 of guides 40, 41 when the operating members arereturned to their first position after an opening operation of thebreaker, whereby the guides 40, 41are pivoted counterclockwise about rod43 and returned to their rst position. See particularly Fig. 5.

In accordance with my invention, each of the operating members 56 and 57is provided with an inturned rigid projection or lug overlapping thecorresponding end of pin 37 which forms the knee of toggle 30. Forreasons to be explained more fully hereinafter, these lugs are arrangedslidably to engage knee 37 thereby initiating switch closing movement oftoggle 30 during clockwise movement of the operating members 56, 57intermediate their irst and second positions. In the embodiment of myinvention illustrated in Figs. 1-6, the rigid lugs appended to theoperating members 56 and 57, which lugs have been identified by thereference numbers 76 and 77, respectively, are disposed tolirst engagethe toggle knee 37 as the operating members approach their secondposition, for example at the point that is illustrated in Fig. 6.

From the foregoing detailed description of the structure of the firstembodiment of my improved circuit breaker operating mechanism, its modeof operation may now be readily followed. Fig. 1 illustrates the circuitbreaker in its closed circuit position. The overcenter springs 52, 53connected to the knee 37 of toggle 30 transmit force through shoulder`36 and pin 39 to guides 40, 41. This force establishes in guides 40, 41a torque in a clockwise direction with respect to rod 43. Clockwisemovement of guides 40, 41 from their first position shown in Fig. 1 isprevented by the latch 42 which engages in its notch 47 the guide roller44.

The circuit breaker isl tripped by rotating tripping shaft 49 in acounterclockwise direction to remove prop 48 from latch roller 50,thereby releasing the latch 42 for counterclockwise movement `on rod 45in accordance with the force exerted on the forward edge of notch 47 bythe guide roller 44. `This action releases the guides 40,141 which arethen free to pivot on rod 43 in ac- `cordance with the clockwise torqueproduced by the overcenter springs 52, 53; As the guides 40, 41 aredriven clockwise by the overcenter tension springs 52, 53, pin 39 iscarried through an arc which intersects the centerline of the springs.The toggle end 38 must follow pin 39 along `its arc, and as pin 39 movestoward its intersection with thecenterline of the springs, the toggle 30is moved in a manner `to pull members 24, 25 of the force and motionamplifying means V21 in a clockwise direction thereby initiating circuitbreaking or4 opening movement of the switch member 16. It. will be notedthat the initial opening movements of the various movable linkages andmembers of the operating mechanism are encouraged and aided by thecompression spring 15 acting through the relatively stationary contact13.

When the guide pin 39 passes beyond the centerline of the overcentertension springs 52, 53, a snap-action switch opening movement of thetoggle 30 takes place. The overcenter springs 52, 53 will now pull thetoggle knee away from the shoulder 36 of guides 40, 41 and move thetoggle links 32, 33 at an accelerated rate to complete the circuitopening operation of the breaker. The open circuit or tripped positionof the circuit breaker is shown in Fig. 4, with the switch member 16resting in its open circuit position on stop 18 and the guides 40, 41stopped in their second position by roller 72 engaging stop pin 71. Itwill be observed in Fig. 4 that the roller 44 located at the lower endof the guides 40, 41 is in engagement with a cooperating surface of thefree end of latch 42, latch 42 being held against roller 44 by theaction of the tension spring 46.

During clockwise pivotal movement of the guides 40, 41, and just priorto the guides reaching their second position as determined by stop pin71, the guide roller 72 engages the lower surface of catch 67 therebytilting the catch clockwise on shaft 69. This action lifts the catchfrom the pin S5 of the operating members 56, 57, thereby releasing orunblocking the operating members which had been restrained in theirsecond position by catch 67. The circuit breaker operating mechanism isnow in condition to be reset.

To reset the circuit breaker operating mechanism, handle member 61 isrotated so as to carry crankpin 63 downward and consequently pivot theoperating members 56, 5'7 counterclockwise on rod 29. Thecounterclockwise movement of the operating members from their second totheir first position drives the guides 40, 41, whose upper surfaces '75are engaged by the operating member pin 74, in a counterclockwisedirection about rod 43 toward their first position. As a result, thetoggle 30 is moved in a manner that produces very little motion in pin31, and both ends of the overcenter tension springs 52, S3 are movedapproximately the same amount.

During the resetting operation, guide roller 44 slides across thecooperating surface of the free end of latch 42, and when the guides 40,41 reach their first position the roller 44 has reached the notch 47 inlatch 42. This permits the latch 42 to pivot clockwise on rod 45 inaccordance with the bias provided by spring 46. The prop 48 is now ableto move into its latch holding position, whereby the latch 42 cannot bemoved counter-clockwise and the guides 40, 41 are held in their firstposition releasably to restrain the toggle end 38 in its latchedposition.

The reset position of the circuit breaker operating mechanismisillustrated in Fig. 5. The circuit breaker s now in condition to beclosed.

To close the breaker after a reset operation, the handle member 61 isrotated to raise crankpin 63 thereby pivoting the operating members 56,57 clockwise about rod 29. The operating members while moving clockwisefrom their first to their second positions carry pin 55 along the arc66. The arc 66 is so disposed with respect to the toggle knee 37 in itsreset position that the overcenter tension spring 52, 53, connectedbetween pin 55 and knee 37, are stretched or charged as the operatingmembers 56, 57 move clockwise. arc 66 is reached at which the operatingmember pin 55 passes through the extended centerline of toggle links 34,35. As the pin 55 moves beyond point 78, switch closing force is exertedon toggle knee 37 by the overcenter tension springs 52, 53. That is, themoment of A point 78 on the 7 toggle end 3S' is pivotally attached is'now in a direction tending to rotate toggle links 3'4', 35counterclockwise on pin 39 and to pull the toggle knee 37 upward asviewedv in--Figs 5 and 6. Such upward movement of the toggle knee, Vwithtoggle end 38 heldin its latched position, wouldl close the circuitbreaker Switch member 16'.

In accordance with my invention, I useovercenter tension Springs 52, 53that are too weak to initiate movement of toggle knee 37 as the pin 55moves beyond point 78 in arc 66. In other words, the static friction andthe inertia of the various movable parts of the breaker will resistswitch closing movement of toggle with a force that is greater than theopposing force applied to the toggle by the stretched overcenter springs52', 53. Among the advantages of using weak overcenter springs havingrelatively low spring constants, as pointed out in the introductoryportion of this specication, are that a relatively small amo'untrofforce is required to charge or elongate the springs during the closingoperation and that the wear and possibility of damage -to the movableparts are reduced. p v

When the operating members 56, 57 have been moved to a position such asis shown by way of example in Fig. 6, the lugs 76, 77 of these membersengage the toggle knee 37. Further clockwisemovement of the operatingmembers will result in lugs 76, 77 carrying toggle knee 37 upward,whereby switch closing movement of the toggle 30-and interconnectedlinkages and members is initiated. The overcenter springs 52, 53, whichhave now been stretched about twice as much as they were stretched atthe previously mentioned point 78 of the operating member pin 55, areselected so that their force is su'icient to accelerate the alreadymoving parts and produce a snap-action switch closing operation. Thus,by using lugs 76, 77 movable with the operating members 56, 57 toinitiate movement of the toggle 30' as the operating members approachtheir second position, it is unnecessary for the overcenter tensionsprings 52, 53 to ,overcome the static friction and inertia of themovable parts, and much weaker overcenter tension springs may be used toeiect snap-action switch closing movement than would otherwise bepossible.

The snap-action switch closing movement of toggle 30, once initiated bythe lugs 76, 77 slidably engaging toggle knee 37, is obtained by theovercenter tension springs L 52, 53 pulling toggle links 34, 35counterclockwise about pin 39'which is releasably restrained in alatched positionl by the latching means previously described. Thismovement causes toggle links 32, 33 to carry pin 31 and hence members24, in a counterclockwise direction with 'respect to rod 29. As aresult, the various parts of the force and motion amplifying means 21are moved in a manner to pivot the switch member 16 clockwise about itspivot point 17 into circuit making engagement with the cooperatingstationary contact 13. The closed circuit position of the circuitbreaker is shown in Fig. l. It will be noted that the switch closingmotion of the toggle is stopped by the shoulder 36 of the guides 40, 41,whereby further collapse of the toggle is prevented.

As the operating members 56, 57 move into their second position, pin 55engages the free end of catch 67 thereby tilting catch 67 clockwise onshaft 69. See Fig. 6. In the second position of the operating members,pin 55 has passed beneath the recess 68 in catch 67, thereby permittingthe catch to tilt counterclockwise on shaft 69 in accordance with itsbias spring 70. Now pin 55' is captured by the catch 67 and theoperating members 56, y57 are held or blocked in their second positionas can be seen vin Fig. l. The catch 67 is rendered ineffective to holdthe operating members only after a circuit breaker tripping operationwhich results in the guide roller 72 engaging Vthe catch surface 73, ashas been fully described hereinbefore. I p

Even if the operating members` 5.6, 57vwere permitted to be returned totheir first position while the toggle end 38 is held in its latchedposition, circuit openingoperation could not result. Thisl is' becausethe toggle 30 is stopped in a position, as is clearly illustrated inFig; 1, such that the extended centerline of the toggle links 34; 35does not intersect the arc 66 of the operating member pin 55. Therefore,the tension springs 52, 53 cannot' be carried over the center of togglelinks 34, 35 by moving the operating members from their second to theirfirst positons, and the moment of the spring force will maintain thetoggle in its stopped position. s

The second embodiment of my invention illustrated in Figs. 7 and 8differs from the embodiment described above in that the inturned rigidprojections or lugs appended to the operating members 56 and 57 aredisposed in a different manner than the lugs 76 and 77, and a mov` ableblocking member and cooperating actuating means have been added. In allother respects the structure of the circuit breaker operating mechanismshownv in Figs.' 7 and 8 is the same as that describedy hereinbefore,and the same reference numbers are used to identify the correspondingparts.

In Fig. 7 the near-side operating member 56 has been removed in order tosimplify the visual representation of the operating mechanism. Theoperating member 57 is provided with a lug 79 disposed to first engagethe toggle knee 37 at a relatively early stage in the closing operation,for example at the point that is illustrated in Fig. 7. It can beobserved that the operating member pin 55 to which is attached one endof the overcenter tension springs 52, 53 has not yet passed throughpoint 78 which marks the intersection of the extended centerline oftoggle links 34, 35 with the arc 66.A In other words, the toggle 30isset in motion by lug 79 slidably engaging knee 37 even before theovercenter springs 52, 53 have passed over the center of toggle links34, 35. Y

The foregoing modification of the previously described arrangementpermits a more even distribution of the force required to move thehandle mechanism 58 during the closing operation. This can be explainedby recalling that the ytension in the overcenter springs 52, 53 isproportional to their elongation, and therefore the force required tocharge or stretch these springs increases roughly linearly as theoperating members 56, 57 are movedV bfv the handle mechanism from theirrst to their second positions. By arranging the lug 79 as is shown inFigs. 7 and 8, the additional force necessary to move the toggle 30 andthe various linkages interconnected ,theretoupon lug 79 engaging thetoggle knee 37 is applied whilethe force required for charging theovercenter springs is still relatively small. Thus there is a relativelyeven distribution of the forces required to move the operating members56 and 57, and it is unnecessary to apply a greatly lncreased amount offorce toward the end of the closing operation. d

As the operating member 57 is moved beyondthe point lllustrated in Fig.7 during a closing operation, lug 79 carries the toggle knee 37 upwards.l Such upward movement of the toggle Vknee is eventually stopped by amovable blocking member 80 which is disposed to engage the toggle kneeand stop the toggle 30 in an intermediate position. The circuit breakerswitch member 16 has not reached its closed circuit position with toggle30 stopped in its intermediate position. The blocking member 8,0 is usedto prevent premature closing of the circuit breaker.

vThe blocking member 80 may be pivotally mounted on the rod 29 which isixed to the circuit breaker frame 11. As is shown in Figs. 7 and 8,suitable bias means" such as a torsion spring 81 is provided to urgemember 80 in a clockwise direction on rod 29. Clockwise movement ofmember 80 is stopped by a pin 8.2 which is aiixed to suitable actuatingmeans comprising for example a lever 83. Lever 83 is pivotally mountedintermediate its ends on rod 43 which is xed to the frame 11. One end ofthelever 83 i s provided' with Va generally U-shaped depression 84 whichcooperates with pin 29 to dene oppo- 9'` site limits of movement of thelever 83. In other Words, the lever 83 may be pivoted or tilted in aclockwise direction on rod 43 until one inside edge of the U-shapeddepression 84 engages the rod 29 as shown in Fig. 8, andcounterclockwise tilting of lever 83 on rod 43 is similarly stopped bytheopposite inside edge of depression 84 engaging rod 29 as shown inFig. 7. The other end of the actuating means or lever 83 comprises anelongated portion having a surface 8S which cooperates with thelaterally extending pin 74 of the operating members 56, 57.

As can be seen in Fig. 7, the pin 82 is disposed on actuating means 83in a manner so that blocking member 80 is stopped in its toggle blockingposition with actuating means 83 tilted to its counterclockwise extremeas determined by the depression 84 and the rod 29. In this position ofthe blocking member S0, a free end 86 of the blocking member extendsinto the path of movement of the toggle knee 37. The toggle knee 37 ismoved from its initial position shown in Fig. 7 to its intermediateposition (not shown) in engagement with the free end 86 of blockingmember 80 by the action of lug 79 as the operating member 57 is movedclockwise about rod 29. The lug 79 is so disposed that it disengagesknee 37 and imparts no further motion thereto while the operating member57 continues moving clockwise after the toggle knee 37 has reached itsintermediate position.

`From the foregoing detailed description of the structure of the secondembodiment of my improved circuit breaker operating mechanism, its modeof operation may now be readily followed. In all respects except circuitbreaker closing, the operation of the mechanism is essentially the sameas that described above in connection with the rst embodiment of theinvention. p

To close the breaker after it has been reset, the handle mechanism 58 ismoved to raise crankpin 63 thereby pivoting the operating member 57clockwise about rod 29. The operating member 57 while moving clockwisefrom its iirst to its second position carries pin 55 along the arc 66illustrated in Fig. 7. When the operating member 57 has moved arelatively' short distance to a position such as that shown by way ofexample in Fig. 7, the operating member lug 79 engages the toggle knee37. Further closewise movement of the operating member will result inlug 79 carrying toggle knee 37 upward, whereby switch closing movementof the toggle 30 and the interconnected linkages and members isinitiated. Shortly thereafter, the operating member pin 55 passesthrough the extended centerline of toggle links 34, 35, and switchclosing force is exerted on the toggle knee 37 by the overcenter tensionsprings 52, 53. The moment of the spring force with respect to the pin39 to which the toggle end 38 is pivotally attached is now in adirection tending to rotate toggle links 34, counterclockwise `on pin 39and thereby tending to close the circuit breaker switch member 16, ashas been explained hereinbefore.

As the operating member 57 continues in its clockwise course, the lug 79moves toggle knee 37 into engagement with the free end 86 of theblocking member 80, whereby the toggle 30 is stopped in its intermediateposition. The toggle is stopped in this intermediate position to preventclosing of the circuit breaker switch member 16 before the overcentertension springs 52, 53 have been fully extended or charged, therebyensuring that no closing action can take place at inconsistent pointsduring the closing operation while less than full spring force isavailable. It should be noted here that the initial movement of thetoggle and interconnected linkages is accomplished at a point during theclosing operation where the force required to charge the overcentersprings 52, 53 is still relatively small.

As the operating member 57 approaches its second position and theovercenter springs have been stretched or charged to substantially theirfullest extent, operating member pin 74 engages the surface 85 of theactuating means 83 thereby tilting the actuating means 83 clockwise onrod 43. As a result, pin 82 affixed to the actuating means forces theblocking member counter'- clockwise on rod 29, and the free end 86 ofthe blocking member is removed from the path of movement of the toggleknee 37 thereby releasing the toggle 3i) for snapaction switch closingmovement in accordance with the force being exerted by the fully chargedovercenter springs 52, 53. The closed circuit position of the secondembodiment of the operating mechanism is shown in Fig. 8.

With the arrangement and operation described above, the duty of theovercenter tension springs is reduced and consequently weaker springsmay be used to effect snapaction switch closing movement than wouldotherwise be possible. This is because the overcenter springs areobliged to move the toggle 30 only from its intermediate position. Inthe intermediate position of the toggle, the moment of the spring forcehas been increased. That is, the arm of the spring force with respect tothe moment center at pin 39 is greater when the toggle is in itsintermediate position than when the toggle is in its initial positionshown in Fig. 7. Furthermore, less force is required to overcome thevarious motion-resisting forces when the toggle is in its intermediateposition, because the toggle links 32, 33 are in a more favorableposition. That is, the toggle links 32, 33 are disposed more nearlytangential to the rod 29 about which members 24, 25 are pivoted, andconsequently the force transmitted by links 32, 33 to pin 31 is moreeffective in moving members 24, 25 and the other interconnected linkagesand members of the force and motion amplifying means 21.

`During resetting of the operating mechanism, the toggle knee 37 rwillmove along a path away from the blocking member until it is below thefree end 86. As soon as the operating members 56, 57 are started towardthe reset positions, the blocking member 80 is able to pivot in avclockwise direction on rod 29 in accordance with its bias until stoppedby the pin 82 affixed to the actuating means 83.

`While I have shown and described a preferred form of my invention byway of illustration, many modifications will occur to those skilled inthe art. I therefore contemplate by the claims which conclude thisspecilication to cover all such modifications as fall within the truespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

l. An operating mechanism for a circuit breaker having a movable switchmember comprising: a toggle having one end connected to the switchmember; latching means for releasably restraining the other end of saidtoggle in a latched position; an operating member movable between firstand second positions at opposite ends `of its normal range of movement;an overcenter tension spring coupled at one end to said operating memberand at its other end to said toggle and effective in response tomovement of said operating member from said lirst to said secondposition to produce snap-action movement -of said toggle therebyproducing circuit making movement of the switch member; and meansmovable with said operating member and engageable with said toggle toinitiate movement of said toggle While said operating member isintermediate said rst and second positions and before said overcenterspring becomes eifective.

2. In a circuit interrupter: a switch member movable between open andclosed circuit positions; a toggle having one end connected to saidswitch member; latching means for releasably restraining the other endof said toggle in a latched position; an operating member movablebetween iirst and second positions at opposite ends of its normal rangeyof movement; rigid means movable with said operating member andslidably engageable with said toggle to initiate movement of said togglein response to movement of said operating member toward said secondposition; and an overcenter tension spring coupled at one end to saidoperating member and at its other end to said toggle and effective inresponse to movement of said `operating member after said rigid meanshas initiated movement `of s'aid toggle to produce snap-action switchclosing movement of said toggle.

3. In a circuit breaker: a switch member movable between open circuitand closed circuit positions; a toggle having one end connected to saidswitch member; latching means for releasably restraining the other endof said toggle in a predetermined latched position; an operating membermovable between first and second positions at opposite ends of itsnormal range of m-ovement; an overcenter tension spring coupled at oneend to said operating member and at its other end to said toggle andeffective in response to movement of said operating member from saidfirst to said second position to produce snap-action switcli closingmovement of said toggle, and stop means `engageable with said toggle tov stop said switch closing movement when said switch member reaches itsclosed circuit position, said stopV means being disposed to engage andstop said toggle in such a position that the forcel of said -overcenterspring will maintain said toggle in its stopped position upon returningsaid operating member to its rst position while said other end of saidtoggle is'in its predetermined latched position.

4. A circuit interrupter comprising: a' frame member; a movable switchmember pivotally supported by said frame member; a toggle havingY oneend connected to said switch member; a guide member connected to theother end of said toggle and mounted on-said frame for pivotal movementbetween iirst and second positions; a latch disposedreleasably torestrain said guide in its iirst position; an operating member pivotallymounted on said frame; a handle mechanism supported by said frame andpositively coupled to said operating member for moving said loperatingmember between first and second positions; an overcenter springinterconnecting said operating member and said toggle and effective inresponse to movement of said operating member from its iirst to itssecond position to produce snap-action switch closing movementof saidtoggle; a movable catch disposed in cooperating relationship with saidoperating member for releasably restraining said'operating member in itssecondv position; said overcenter spring being effective in response toguide releasing ioperation of said latch to drive said guide to itssecond position andl produce switch opening movement of said toggle; andmeans responsive to movement of said guide into its second position toengage and move said catch thereby releasing said operating member.

5. In a circuit interrupter: a switch member movable' between open andclosed' circuit position; a toggle having one end connected to saidswitch member; latching means for releasably restraining the other endof said toggle in a latched position; an operating member movablebetween first and second positions at opposite ends of its normal rangeof movement; rigid means movable with said operating member and slidablyengageable with said toggle to initiate switch closing movement of saidtoggle in response to the movement of said operating member toward saidsecond position; an overcenter tension spring coupled at one end to saidoperating member and at its other end to said toggle to exert a switchclosing force on said toggle as the operating member moves toward saidsecond position; a'movable blocking member disposed in the path ofmovement of said toggle to stop switch closing movement thereof beforesaid switch member reaches its closed circuit position;-and actuatingmeans movable with said operating member and disposed to actuate saidblocking member as said operatingv member approaches said secondposition thereby releasing said toggle for snap-action switch closingmovement in accordance with the force exerted by said overcenter spring.

References Cited in the iile of this patent UNITED STATES PATENTS1,753,975 Welch Apr. 8, 1930 2,188,949 Jackson Feb. 6, 1940 2,692,926Cole Oct. 26, 1954

